The zigzaggers are on e-bay; I think
#160986 is for slant shank. I have the low shank version for my 201, but I can't say I have use it a lot. If I need to zigzag it's either my Bernina or my Elna. I love the buttonholers for my 201, I have the green plastic box, the dark maroon box is for slant shanks.
This one is so far worth the price, it has the extra templates. There are several type buttonholers for slant shanks, I think they all should work on the 301. I think there's a blind stitch attachment for the 301 too.