Links below are to heated gear of one sort or another. The gear ranges from liners and undergear to full suits and includes items such as grips and seat heaters. I'm not endorsing anything on the list, was just cold and began researching!
I personally have used a pair of battery powered gloves and they worked fine in 20 degree F weather on an unfaired bike. But you need to learn how to use them as the heat is in the palm area only. Plus battery powered means you better have a supply of batteries. Cheap batteries can be done in an hour and good ones can sometimes go 4-5 hours. Rechargables seem to hit the middle.
If you opt for plug in gear then make sure you know the power drain total and your bikes output. Be careful as most bikes output is at max at a higher RPM. For example a 1981 GL1100 puts out 300 watts at 5000 rpm. How often are you going 5000 rpm?
Some of the companies linked also sell motorcycle gear other than heated so check them out.
Also, if you have a circulatory problem or diabetes you
should probably talk to your doctor first.
HEATED CLOTHING (Just
clothing)
Gerbing
Jackets, pants, gloves, socks, custom suits, wiring harnesses and adapters, and controllers. Plug in. Supplier of Harley heated gear.
Chilli Heated Clothing
Limited
http://ds.dial.pipex.com/chilli/
British version of heated waistcoat (vest) (no collar) and controller. Plug in.
Widder
Vests (collared and non-collared), armchaps, gloves, and controller. Controller is said to be the smallest on the market. Widder appears to have been the first to make the gear for motorcyclists. Plug in.
Kreamer Outdoor
Vest, glove liners, insoles, jacket liners, neck gaiter, heated long johns. All can be heated via battery packs or 12v power source.
At-Last
Vest (regular and tall, no collars), seat pad, warming belt (wraps around the waist), controller. Plug in.
Gorix
http://www.gorix.com/slider-index.htm
High tech heated clothing. The cloth is conductive and doesn't need wires running thru the clothing. Has some motorcycle stuff listed (jackets mostly) but no prices or pictures. Plug in. Listed elsewhere are vests, coats, underclothing, full suit w/ gloves and hand muffs.
Gear Shoppers.com
http://www.tgoemall.com/mallbodywarm.htm
Links to many different battery/heating pack warmed clothing.
The Glove Liners
http://www.electrichandwarmers.com/glove.html
Glove and insoles, battery operated.
Extreme Comfort
http://www.extremecomfort.com/cgi-bin/xtreme/heating#glove
Glove liners, insoles. Battery powered. Same as The Glove Liners above.
Harriet Carter
http://store.yahoo.com/harrietcarter/heatedgloves.html
Battery powered gloves
Gr.8 Designs
The Cassiar Vest and controller. The vest uses the gorix material spoken of in another link here. Plug in.
HEATED CLOTHING, GRIPS, ETC. (Assorted but includes clothing)
Aerostich
http://www.aerostich.com/riderwearhouse.store
Vests, jacket liners, grips, grip tape, seat heaters, heat packs, accessories. Plug in. Also a great amount of non-heated gear and suits.
Giali UK
http://www.motorcycle-uk.com/giali/Gialiheatedclothing.html
Jackets, vests (called waistcoats), harnesses (looks like a sideless vest), gloves, trousers (nice model! *grin*), socks, neck warmer, kidney belt, and overgrips. Plug in. Plenty of other non-heated gear also.
Custom Heated Headlines
http://www.customheat.com/chalkbd/index.shtml
Grips, vests listed but no info on web site. Seems to be the same site as Custom Heat, Inc. below.
HANDS (Just things to keep the hands warm)
Custom Heat, Inc.
http://www.customheat.com/main.shtml
Grips
Hot Grips
Grips and controllers for motorcycles, atv's and snowmobiles.
Heeters
http://www.heeters.com/snbgrips.shtml
Grips, grip heat tape. Intended mostly for ATV, snowmobiles, could probably be adapted.
Calamander, Limited
http://www.calamander.co.uk/heated/glovesandgrips/glovesandgrips.htm
Grips and heated glove liners. Plug in.
MISC and KITS
Bodywarmer
Appears to be a wire harness worn under clothing over the underwear. The harness extends straight down from the shoulders to the feet. Does not extend out on arms. Comes with in three configurations; two hour batteries, four hour batteries, or 12 volt. The battery versions recharge on household (110 volt) circuitry.
Kustom Komfort
Kits to make your own heated clothing. Controller also.
Procom Electronics
Kits for wiring your own jackets, chaps, pants or full suits, along with Controllers. For information e-mail PRO2000HEAT@aol.com
Internet BMW Riders
http://www.ibmwr.org/otech/heatedclothing.html
How to make your own heated clothing.