I only have a 13710 - but I do like it and am considering another higher-end model, and then also a mixed badger/horse brush.
Horse Shaving Brushes - Gifts&Care
Gifts & Care have been active here as vendors here in the past. The only issue is that once you get past a few items (500g??), then the cost of postage rises quite high. That issue is with the Spanish postal service who charge like AusPost does - not with G&C.
They offer a custom brush service in conjunction with Vie-Long. I find that they have plenty of backbone so shorter lofts are unnecessary. I'd love to get a larger diameter knot - say 24mm - but they do not offer that as yet, just loft changes.