I would personally shy away from the valves in the second link, and I would not use an ASCO 8219G094 for natural gas service.
How much pressure are you providing to the valves?
For a 1/2" valve have you looked at the ASCO 8030G069
? (0-8 psig)
They list for $168 brand new, and are from a manufacturer who has been around for over 100 years.
If you need high pressure the 8210G075
is good for 0-50 psig.
These list for $184 each.