Extension To Air the Spare

A few months ago I saw where a trailer owner had installed a valve extension so he could check the air pressure in his spare tire, that was mounted under his rig,without crawling under.

Being as I need to crawl under my fiver to check the air in the spare, this seems like a mod that I would put to good use.

Anyone have any ideas where to get the parts, or an assembled unit ?
I would need an extension about 3' long.