Need to extend shut off valve stems

[branimal]

My shut off valves stem lengths are too short to reach into the vanity.

Is there a way to extend the existing stems? Sweating on longer stems is a last option. Wanted to know if there is simpler way.

 

[branimal]

I'd like to buy or fabricate some type of extension handle.

Do plumbing supply stores sell an adapter that can extend the handle?

See the flats on the stem in the first pic and the cut out on the handle in the second pic.

I could ask a welder to cut the handle down to about the size of the stem and then weld on an extension handle.