Make your own slides on any dimension aluminum extrusion. This slide is simple to print, and easy to assemble. It uses a combination of printed slide surfaces and RC car bearings for very low friction. Use a pair of them with your carriage. I am running them on my Pocket Printer with good results.
Print in pla, which has very good wear characteristics. You may need to make some adjustments to the dimension of the printed slide surfaces to get the fit you desire. The dimensions between the bearings is 0.2 mm less than the extrusion width. The slide flexes slightly to give a preload to the bearings. You can adjust for you own preferences.
See the pdf assembly drawing for critical dimensions and instructions. There is also an exploded view of an application on the Pocket Printer page.
Use 623ZZ bearings (3 x 10 x 4), you can get a 10 pack for under $10. You also need M3 x 20 screws and 3 mm washers.