I had a problem recently with isolation of my TT. . . . 'me being me', I decided £20-£30 quid was lot when I could make something.
I cut 3, 1.25" squares from a 1" plank of mahogany, drilled a 5mm hole in the middle, taped it out to a 6mm thread. Screwed in a 6mm dumpy spike and a lock nut . . . perfect inverted wood spike support, and they are adjustable. My efforts do not look so posh as the Russ Andrews offering, but then they are out of sight.
CJSF