
A cheap and easy way I found is to take a standard set of tiddly winks (the set I have is actually quite nice, but if you can find a really cheap set, that's fine too). Instead of tracking down actual warhammer miniature "shields" (or something from reaper miniatures at similar cost) which are intended to be glued to the fists of these figures, I thought of using buttons, or maybe small poker chips, even coins, but these look to be an even better match.
Standard Tiddly Winks has three sizes of discs in the bag: the big ones you shoot with (called squidgers), the standard size (nickle size?) ones we all think of and then the smaller (dime size?) ones. The small ones seem just about right (I don't have special calibers to measure). Instead of gluing it, I figure I'd use poster putty (know variously as sticky tak, poster tak, originally blu-tak).
I don't even have to paint the discs! Instead I can pick a color (red, blue, yellow or green) as a colorful shield for the regiment. Granted, they are all round as the only choice of shape, but that's fine. Many scans exist of the shield designs but others can easily be found online and printed off either on sticker paper or regular or glossy paper and glued (I prefer sticker paper). With my previous efforts to "restore" my beat up BattleMasters set I printed the shield images on sticker paper and then put a clear layer of tape over them to protect them a little more (printing on a gloss surface wasn't practical). Previous efforts to attach regular paper with gluestick didn't work well, and I didn't want to prime the figures nor did I wish to simply remove all the stickers and try to paint little designs with a brush on the plastic. I probably will use brand new designs for the new regiments or maybe just find some images online I like and use those for the "shield stickers."
So here is the first step but I'm pleased how its turning out so far, and I can always change my mind easily with these mods.
Yes I know the figure below (a plastic warhammer fantasy skaven) is clearly modified for HEROQUEST (note the square base). But I have some figures "on order" that will be getting the above treatment that have the familiar "slot-a-base" (slottabase?) design on the bottom with the tab, in this case a regiment of dwarves. They should slot easily into any spare BM unit tray (the only trick is removing any glue to de-base the figures I've got, probably try simple green or LA Awesome right? assuming water and gentle pressure isn't enough).
There are images all over that could be used for shield graphics, and you can easily make your own. I find a discussion here that had collected some cool ones. Print to the size you want and trim as needed with a scissors.