You don't even need him to be frank. Go to any high street optician and get a free test (or use your current prescription) then go to pretty much any online reglazing shop and send in your inserts. Plenty of companies do inserts for loads of their goggles - I use ESS V12s. I think with the goggles, inserts and scratch resistant/anti-glare, thin lenses I paid about 80 quid. All in all it took about 20 minutes of clicking to do online.
1. Find some goggles you like the look of
2. Find inserts that fit them (the majority of the top brands make their own for their goggles and glasses and they cost about £10-20)
3. Send off the inserts to a re-glazing shop like
GlassesDirect with your prescription attached
4. Wait for the post to arrive (mine took a week)
I too went to Tactical optician, but I didn't like the selection of goggles and thought many to be rather overpriced. It's a professional service I'm sure, but reglazing frames isn't rocket science, and so long as you've got your pupillary distance as a part of your prescription (which all highstreet retailers will provide to you if you need it, and you can even do it yourself if required) then you'll be golden and save a bunch of cash.
Couldn't be happier with mine. Haven't had a single issue with them.