General advice I have seen given in articles on this site (and others) means you’re in the right ball park. You do want to be buying cash-like things, but apart from the rules on prepaid VISA/MC not allowing purchase with other cards, they also come with a large fee ($5+/card).
You’d be better off trying to bring forward your spend on certain categories. Buy some supermarket vouchers from the supermarket. Supermarkets also sell vouchers for many other categories. This article has a list of vouchers that can be bought from supermarkets http://www.pointhacks.com.au/american-express-supermarkets-gift-cards-bonus-points/ It was originally written for how to achieve triple points per dollar at non-supermarket retailers, but the list of vouchers is useful to your current situation I believe.
I have also helped our family members I have referred to a new card, that found themselves in your situation, by allowing them to pay bills in my name using their card, and then I’ve repaid them in cash before their card statement was due. Perhaps you have family or friends with more expenses than yourself who would allow you to do this?