Hmm, parents... they can be such a pain, can't they? :/
Can't you ask to split it, so you also have your share? That often gets my parents more lenient to allow things anyway.
Or can't you say you need it for... a sport you do? So the "good ones" don't break?
How much do the glasses cost?
I guess having them for a month or so and then letting them have a little "accident" is way too obvious, right?

I don't even know if I could do that myself (too damn honest) but if it's your only road to new glasses...
But yeah, don't worry too much. They could be better, but they aren't overly feminine or anything that they will blow all your chances of passing. If you either present more andro in general, or go way more masculine with the rest, I think you'll still pass!