I have been seeing replacement anodized aluminium parts for the Prusa MK3 printer stock PETG parts online, but the price is typically a bit steep and I couldn't find any reviews. A couple weeks ago I found some Y axis parts at a reasonable price and thought I would take a chance. They arrived a few days ago and I have to say the fit and quality is really excellent. I am now replacing the Z axis PETG brackets and will likely replace the X brackets as well. This is simply motivated by mitigating points of failure as well as generally stiffening up the frame and all axis in order to get as good a print as the technology can deliver. For anyone interested in the Y axis upgrades the sellers name is WillBest on Amazon. For the Z axis I ended up ordering the parts from two other Amazon sellers, GIMAX and KIMME SHOP, although I have not received the parts so I can't say whether the quality is as good as the ones from WillBest.