Rachel Lawson@rachel@norfolk.social
I should probably have mentioned Iām in the UK
John Timaeus@johntimaeus@infosec.exchange
@rachel@norfolk.social
I've got a couple, but US based.
You can get plastic training ones fairly cheap.
A good alternative is a demicross which can be knocked together with a couple of measuring sticks, or paper bits taped to a large construction square (used for plywood or drywall).
https://en.wikipedia.org/wiki/Backstaff (about halfway down)