You're looking for M&A lawyers, presumably pedigreed (from a large firm with a well regarded M&A practice, for instance). Your normal contracts counsel should have good thoughts about referrals.
Look, at the point where you're selling a company in a multimillion dollar transaction, some of these excuses go out the window. Get a lawyer, and then ask your lawyer for a referral to an M&A practice. Company acquisitions are a shitload of specialized work; it's honestly weird for me to hear that a general practitioner handled this person's earnout contract.
It's not an "excuse". I'm surprised that you've never seen bad lawyer referrals. You honestly haven't? (and I'm not talking about general practitioners).
I've also seen a (pedigreed) General Counsel that sank a tech company.
Honestly pal, if you’re in a position to sell a company for the kinds of dollars that PE deals with, you needed a lawyer a long time ago. I understand that they’re expensive, legalese is intentionally difficult to understand and lawyers aren’t builders so they’re not worth funding. I understand those excuses because I’ve used them.
But you needed a lawyer a long time ago. If you actually don’t have someone who deals with contracts, terms and things like that, fix that first.