Ah...too bad.
I am a musician, and I understand. There are very good amateur lines of products that most music stores carry.
However, for pro-audio and professional recording gear, one often has to dig a little deeper.
Windsor-Newton is professional stuff.
Back in my days at Art School in Boston, we would have to go all the way to Cambridge to a place called “Charrette” to get out Graphic Design Supplies.
That was over 40 years ago, so I don’t know what the designers do now.
Gamblin is another brand of oil paint that I use for certain colors. I didn’t see it but I will look again when I go back for frames.