Where do you buy the rubles from, all forex brokers announced that they are suspending ruble trading for the moment.

Exactly, and that's why the apparent discrepancy is there. Pretty much any time there's an apparent large arbitrage opportunity one will find that there's a barrier (or significant cost) to actually executing it, or it already would have been arbitraged away.

If you want to buy rubles with USD how do you propose to do so without kayaking your way to Russia first?

USD => Chinese Yuan => Russian Ruble?

If you feel that the risks associated with evading these sanctions are worth the gain then you are a lot braver than I am, and besides that I would not want to profit of all this misery anyway.

Chinese Yuan is an extremely unpopular currency corridor because a) there is no market for it, it’s effectively a peg and b) it’s divorced from usage in the country it’s supposedly from.

That is to say you’ll pay a gigantic premium on that trade.

Ok, so you'd end up flat at best and the whole thing would be a wash dollar wise while still putting you on a bunch of watch lists. Is that what I'm getting out of this?

I don’t know enough about that particular corridor to know what the specific outcomes would be.

That said, my impression is that flat would be tough and liquidity would be a real problem.

Find an answer to that question to collect a tidy profit ;)

The Bering strait isn't that wide, come on.

Good luck actually executing that trade

I don't think executing the trade will be all that hard, the settlement could be though.