You can make your own extentions if you can find a place that sells machinist tools. Buy a 3/8 swivel or two,for extentions on a mag base for dial indicators and a piece of 3/8 drill rod or cold roll 3/8 rod. Most shafts on vise's are 3/8. The cost's are not very much, and you may find these things in a flea market where some people sell tools even cheaper than a tool supply.
Cut them any length and you can also bend them any shape by heating. Also they have a 3/8 to 1/8 swivel you may use to make your own parachute hanger or bobbin cradle. I use a 1/8 stainless welding rod for this, any 1/8 rod will do though.
Jesse
In old age walking on a trail of beauty, living again may I walk.