Cheapest option would be a giant cardboard box you have lying around. Followed by a grow tent. Both go up passively to around 45C which is fine for ABS. They are working well for the occasional abs print. If you want something more professional you can diy an enclosure, prusa has the step files for a version build of ikea lack tables on printables. Many similar lack versions online You could replace the acrylic side panels for anything you have in your garage to save costs. In the end you can modify any box to be your enclosure. Last but bot least there are full acrylic enclosures out there, even in custom sizes. Those look great but will come at a price. Dont forget that any pla printed upgrades for your ender will soften and loose proper function. Also electronics should be moved outside to lengthen their lifetime.