First off, it’s healthy to temper your expectations. “Affordable” is very much a relative term. You can find general practice attorneys who can do it, but they can make half million dollar mistakes as in the source article. It might have been an $800 or $1000 difference an hour, but you can get a lot of those hours for $500,000. I’d expect to pay more than any reasonable human would charge for an hour of their time. It sounds negative (and it is) but this is about health.
You’re looking for a highly specialized practitioner with practical M&A experience. I’d start with my regular counsel (aka the person who does things like terms and conditions, contracts and the like) and ask for a referral.
It’s also really useful to ask people who work in the same field as you and who have been through an acquisition. I wouldn’t necessarily trust them for a skills based referral (ie - Lawyer A performed wonderfully) since they’re likely not lawyers and you often won’t know you got bad advice for years. But I would trust their opinion on things like how the attorney communicates and manages the entire process.