The DPA UA0896 is a good affordable windscreen that fits the M300s and worked nicely with them when I had that setup. I think you'd have to spend quite a lot more to get significantly better results, or use them as a base for some DIY Ratcoats Furjammers.
I ran my M300s in X-Y at or near 90 degrees most of the time I used them, and I couldn't tear myself away from that setup since it worked so consistently well. If I was running them today, I'd give them more chance in ORTF and DINa.
- Jason