Need a belt for Sony WM-F15, or a good link to buy belts for different sony walkmans.

Its the same 0.9/0.9 mm thick 49mm dia belt (Sony spare :Sony 3-315-405-00) used in these models and my 'favourite' belt :
Sony TC-WE305
Sony WM-50
Sony WM-F10II/F10/
Sony WM-F65
Sony WM-10/20/30
Sony WM-70
Sony WMF13
Sony WM-F70