I run a small seven figure revenue business and I have paid more than one open source maintainer/contributor for work done. Definitely don't be afraid to ask; but I usually offer upfront. I'm an ex-developer so I usually offer the help I can with the keyboard, but know that it's limited compared to most of the really good developers out there maintaining a real project, so I offer time + money.

The problem is getting single open source maintainers to commit - and followthrough - with support. They are often way too busy with their job to actually be professional with support and adhere to even a loose SLA.