eBay listing for a step up ring - this makes the barrel look "factory"... soes not change the profile at all..... just make sure you use a slim 40.5mm filter so you do not get any vignetting...

eBay Seller - HEAVYSTAR  http://myworld.ebay.com/heavystar/?_trksid=p4340.l2559

New 40-40.5mm Step Up Ring 40mm-40.5mm 40-40.5 Canon RF - $6.95 U.S. plus shipping ($3.95)

Then you might want a clip-in lens cover...40.5mm Snap-on Front Lens Cap for Canon Nikon Sony $4.39 Free Shipping

eBay Seller - onibuy - http://myworld.ebay.com/onibuy/?_trksid=p4340.l2559

___________________________________________________________