Glad to hear you might get what you want. Prices will depend on which country you are in (likely to be cheaper online than in a shop). I'd advise getting a softer squishy dildo rather than a rigid hard one. In my experience, hard means pokey and uncomfortable - and not in a good way - but I have used a softer jelly-like one that is very enjoyable but can still be used hard and fast to good effect, without causing damage. It will not feel squishy when it is inside.

Also, will this be your first time with a strap-on? Even if it isn't your first time with it, sounds like it will be her first time using it. Might just be me, I'd be slightly worried about doing it for the first time with someone who is angling to be very aggressive with it. Being penetrated without being warmed up can be very painful, and not in an erotic way. At least make sure that if you ask (maybe with a safe-word), she will take it back out immediately. In my experience, if there is any pain it will be upon initial penetration. Once it's in, she can usually be as aggressive as she likes. Oh, and a towel/lots of tissues around the place is probably wise, as the end result can be a bit messy

All that having be said, hope it happens and that you enjoy it! I hope to see a write-up (or perhaps a story?) afterwards.