Marvel Precision, the company that makes top flite 1911 .22 Conversion Units now sells replacement magazine springs that will fit Colt or Metalform magazines. Cost is $6.00 each + shipping. You have to call or email to order. The replacement magazine springs are NOT listed on their website. I've ordered 4 and will update this thread after I try them. I haven't found a source for these springs previously. I did purchase one of Wolff Gunsprings generic .22 magazine springs and installed it in one of my Colt magazines and it didn't work worth a damn. Marvel Precision also sells plastic replacement magazine followers that have a steel insert for the slide hold open. They are $14.00 each + shipping. I have several of these and they work like a charm.