Mr. Heater Gas Valve Problem

I have a Model No. MH25NG Item No. F272200 Mr. Heater in my garage. https://www.amazon.com/dp/B00006L7UZ/?tag=fabo03-20
I installed it about 10 or 12 years ago, and it's been fine until the last coule of years. The gas valve needs a tap on the side for it to operate.

This link says it's discontinued. VS820A1039 by HONEYWELL - Buy or Repair at Radwell - Radwell.com Searching shows other valves that will possibly interchange? Some cost more than a new heater. ($300 ish)

Can a gas valve be repaired? Is it sticking or? I've never worked on one.

I'm a capable mechanic. I just don't want to blow up my garage. :rolleyes: