Firstly, I'm sure many of us can relate to how you must be feeling but good on you for otherwise being up-beat about your appearance and appeal to others on RedHotPie. Hey, those sexy T-Girls can be ultra picky so if you're getting their attention, you're on a good wicket.
Your concerns are no different to those of many women who rely on everything from push-up bras to super stretchy underpants to reign in post-baby bellies in order to disguise whatever they deem as being imperfect. Of course, a person's hair or hairstyle is probably more likely to get scrutinised on a first date so I understand your conundrum about 'fessing up before meeting or leaving it for much later.
I would suggest that you don't need to be upfront about wearing a wig (or other less obvious additions other people may have such as glass eyes) before you meet someone new. Just see how things go on your first date. If there isn't mutual interest anyway or interest is one-sided, then there's no need to elaborate.
If conversation flows well then perhaps the topic of your accident may come up, in which case your date may come to her own conclusion without you even mentioning the wig (yes, she may have suspected it if you admit that it's not unnoticeable in person). If she's still none the wiser, then at least you've opened up an avenue to discuss the wig later if need be.
If you really hit it off and decide to progress to the bedroom then that's when I think you might have to make mention of your wig, although if it's not likely to fall off or move about during energetic sex, you needn't be concerned either. If the wig doesn't generally work well with vigorous activities, then you are better off letting your partner know about it beforehand then have it fall on top of her mid-thrust. If that means putting off sex until you can suggest a second date to explain things, so be it.
Overall, it is important to be honest but often times it's all about trying to impress people physically first on RedHotPie so you'd be forgiven for not mentioning something that isn't really that detrimental to two people who are otherwise very compatible from having a good time.