Here are the results for 'Walker' on the Scottish Tartans Authority website:

http://www.tartansauthority.com/web/...atus=firstload

It looks like the Walkers are a sept of MacGregor and maybe the Stewarts of Appin. It ALSO looks like someone registered a few Walker tartans in 1993 and someone else registered one in 2003.

Please note that just because these tartans EXIST in the STA Database does not mean that they're all readily available as 'stock tartans' from any mill. Most of the MacGregor ones and the Stewart Appin tartans are readily available, but none of the major mills stock the Walker tartans. They CAN be specially woven, but the price will go up.

Hope this info helps!