Keep searching CL. @$300 you're not going to get very much bike at the LBS, and doubtful it'll hold up for very long.

A buddy of mine started at 396# two years ago at the Fully Loop, now in the mid 200's. Keep at it, and biking will pay off. He originally went with a middle of the road mtb hardtail, and still blew up rear hubs and spokes until finally settled on a custom wheelset. Be prepared, it's not easy nor cost effective if you go cheap initially.