Here are some of our favorite low cost linear rail vendors. Let them know we sent you!
MGN12/H
Amazon USA
RobotDigg
(Stainless)
https://www.robotdigg.com/product/766/Quality-440C-SUS-MGN12-linear-rail-with-carriage
(Black)
https://www.robotdigg.com/product/1314/
MGN9/C
RobotDigg
(Stainless)
https://www.robotdigg.com/product/779/Quality-440C-SUS-MGN9-linear-rail-with-carriage
(Black)
https://www.robotdigg.com/product/1314/
AliExpress
https://www.aliexpress.com/item/32789407263.html?spm=2114.12010612.8148356.1.53637f7bLN3NPJ
Amazon USA
https://www.amazon.com/gp/product/B018KFFTIO/