Stake and Sportsbet are the only ones I know who can handle that much in a bet. If you're looking to get that much weight around in sports betting, and have tried these two, there's no other way but to play on fiat sportsbooks, though their rules are sometimes unlikeable, and you don't have that much 'freedom' compared to what crypto sportsbooks offer.
There are reputable crypto sport books that can handle large bets just like stake which I think do not have anything like maximum deposit or withdrawal. It is good for us to ask questions when we don't really understand the decision we are taking. And for us to have a better understanding about crypto sport books to know which can suit our demand, it is good to aks questions so that those that had used the casino can always come and give us hits.
seems that the OP is still asking for a reputable site. why not start from smaller bet and see how the casino/bookie will treat you as a player. but it is better to stick to known reputable sites rather than risk to a new one. wonder why the OP is getting out of stake? stake is one of the biggest bookies out there which can handle multi million dollar of bets. very few can handle such amounts.