Any second-hand business-grade laptop (Lenovo Thinkpad or Dell Latitude) on eBay will do. VCDS and other diagnostics software isn't resource-heavy at all so you

Any second-hand business-grade laptop (Lenovo Thinkpad or Dell Latitude) on eBay will do. VCDS and other diagnostics software isn't resource-heavy at all so you can actually go much lower than 250 bucks if needed (and spend the difference on a solid state drive and potentially new battery?) However if you have an Intel Mac I suggest you give virtualization a try. It's gone a long way since the early days and I would bet good money it will work just fine in a VM with USB passthrough.