This has actually been done rather often in the past, you can start a donor driven PAC that can compete with corporate lobbyists with crowdfunding. It's generally quite a bit cheaper too because while we all love to criticize politicians for only listening to monied interests if they can raise some campaign funds and get brownie points for their voting base they're happy to dramatically spurn the corporate funding they'd otherwise accept with open arms.

Honestly though, actually reaching out to your representatives and talking to them is far more effective than most people assume.