something like this? [ebay picture]
yah, you can get one thru any bike shop,
3 sizes, .833" [bmx]
22.2mm/7/8" that is what you need,
and 9/8"
I got a long Chromo 25.4/1" seatpost thru Redline, cheap, strong . chromed.
needs a clip on top for the saddle. and shim to fit the seat tube ID on the bike ,
but pretty darn strong ..
you can find those as 1" is a common shim ID to work from..