I just put my '76 Sachs Colombia on the road after sitting for about 10 years (and before that, sitting about 20 years). Needless to say, the tires are severely dry rotted. I've been looking online but would like to find something local as I'm not sure how much longer these tires are going to hold air on my daily Comm Ave. construction trek. They are 17"x 21 1/4 (I think) and ideally I'd like to get whitewalls but will settle for anything that holds air. I just got laughed out of Bicycle Bill's in Allston. PLEASE HELP!!!