I don't know of a shop for you but the math on your economics doesn't really work well. You're saying that you can earn 5% a month and want 80-90% for yourself. So if I'm your prop shop, I earn 10-20% of the 5% = which is about 6-12% a year. In return, I need to backstop your strategy which includes being short options. If another Global Financial Crisis spikes vol, I run the risk of losing more than the $450k I put up as collateral if the short options positions skyrocket and need to have faith that your hedging is good. I don't know of anyone willing to collateralize an options short selling strategy where their best-case ROC is 10%/year. There's a reason that hedge funds are 2/20 and not 0/90 -- I suspect that if you find someone who'd be willing to accept a 50-50 profit split, you should jump on the opportunity.
Short options are spreads. portfolio is always fully hedged. That changes the economics back to something viable. Doesn't matter anyway. Prop deals are easier to come by with 500k instead of 50k. Maybe later...
As mentioned by another, Towertradinggroup with HQ in London can probably do that if you have track record. You're essentially giving up % of split for leverage.