Honestly, I'm surprisd you all search for parts first. I have a copy of the parts manuals (maybe that's why my process is different), and look in them for the #'s.
I then send an email with quantity and part number and description to them.
If they're out of stock or don't have anything, they tell me, I thank them and they order what they DO have. Don't even have to GO to their site.
In very few cases I could not find a part number in the parts catalog, and would send an email with the description, and a part number that's similar and explain the difference, and they have (in perhaps 90% of the cases) found what I needed and shipped it.
I also stopped by their place, and was freakin' blown away. Aisles and Aisles of NOS parts for freakin' EVERYTHING. Plus the machines to make more. And parts they don't advertise or have on their website - I picked up an NOS Nudge-It playfield just on a whim - one email I sent was jokingly, 'You wouldn't happen to have an NOS Nudge-It playfield?'. And the reply I got back was, 'We have one. Want it?'