I wouldn't worry about it. I have never played a game where people told me I had to wear contacts instead of glasses.
I'm going to wear my usual glasses, plastic and all. I can't wear contacts for long periods of time.
I think it sort of falls under a safety thing.
IF however, it is very important to your personal immersion, there is an excellent website where you can get super super cheap prescription basic metal frames. (Zenni Optical)