I don't know of any specialists in that area
Whilst $1000 seems like a big quote, the bulk of that would be labour. It's usually a writing fault on these and not the hall sensor itself.
The Volvo dealer should at least be familiar with dismantling the car (without breaking trim) to get access to the wiring and have access to workshop manuals and diagnostic procedures that most independents don't.
I doubt anyone else would be prepared to give you a solid quote on the repair.