Fortunately you can make your own insulators. Chances are you already have the materials. Personally I use plastic kitchen chopping board material. Here's some further ideas.
* KC8VWM's pictorial article on QRZ forums
* NZ Radio Guy's use of conduit (video)
* Kevin Loughin's idea for insulators (video)
* KD8RTT's cheap source of insulators (video)
PS: The items below may assist your experiments. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.