If groove size is a problem try this 10x10mm Parting Bead Channel / Carrier for use with 8mm direct fit parting beads.
Will take 8mm Direct Fit or Double Flipper Parting Bead
The channel screws into the original parting bead groove to provide a locator for the parting bead seal.
A Groove size: 10mm
B Groove size: 10mm
Standard Colours: Brown and White
Sold in 3m lengths