Adapter to turn a vent rib into Weaver style or a Picatinny style base?

[Radiohead]

Hello,

I have a 12 gauge shotgun on which I would like to mount a red dot scope. Anyone know where I can find an adapter to turn a vent rib into Weaver style or a Picatinny style base? The rib is 5/16" wide.

Here are three example available in the US but not in Canada:

1) TruGlo scope / Red-Dot mounting adapter, SKU# TG8953B http://www.truglosights.com/IW_Products.m4p.pvx?;MULTI_ITEM_SUBMIT
2) AimTech Rib Rider, UPC# 3572403004 http://aimtech-mounts.com/Rib%20Riders.htm
3) B-Square Shotgun Universal Cantilever Mounts - Ribs up to 3/8", Product # 16175 http://secure.armorholdings.com/b-square/uni_mounts.html

I am open to suggestions.

Thank you,

 

[dizzy]

I took a file to a weaver rail and mounted an aimpoint to a ruger 10/22, it wasn't perfect so rezeroing was an issue when removing and replacing but it worked very well. $11 for the rail I think and a few minutes on the grinder (electric file)

 

[Radiohead]

Thanks for the idea. I decided to try this adapter for $11 (shipping included) off ebay.

http://cgi.ebay.com/Spiderfire-raising-mount-base-20mm-weaver-rail-M087-/280561118307?pt=LH_DefaultDomain_0&hash=item4152beec63

For $11 if it doesn't work then it's no major loss.