I'll give you the names of brands that are GMP and quality:

NOW (makes P5P)
http://www.iherb.com/Now-Foods-P-5-P...1&sr=null&ic=3

Solgar ( Metafolin) online mostly.
Doctor's Best:
http://www.iherb.com/Doctor-s-Best-B...3&sr=null&ic=1
this is a fairly new product and very affordable and quality.

Jarrow: (methylcobalamin).
Puritan's
Doctor's Best

Make sure you take the B12 on an empty stomach so it is absorbed properly.
And you don't need the high dose of methylfolate that is in Metanx. Start at 800mcg.

I am using the Costco generic now for my methylB12. It works out to 6 cents a day.
But I previously used Puritan's 5mg and was tested after 3months with very high levels. So I know that worked and was absorbed.
Methylcobalamin is making its way into stores locally, finally.
The other two less likely locally, and better online.
iherb.com and Amazon both have highly reduced prices.