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I'm not sure if you can get them separately but what about the grenadier barbarian orses available from mirliton. They might do a special order? http://www.mirliton.it/index.php?cName=fantasy-2528mm-barbariansAlso ebob does lots of horses. I have some grenadier ones if you want a scale shot(still using them sorry)
I can't be super helpful, but I can say that Gripping Beast Dark Age cavalry will be far too small for you then. They are a little bit slighter then Perry horses, and I've used them for light cavalry in my Game of Thrones forces.Fireforge could be ok if the tack suits you, they are about a size with Perry, maybe a hair beefier.
Fire forge might be the ticket. I have a box of the mongols to remount my old Kislev horse archers on.
Yeah, they aren't too big. but are beefy for their size. Riders are separate which is a bonus. Shipping is horrendous from them. I've wanted an order for a while, 80 Euro order costs 40 Euro to send. I am in New Zealand though so shipping is always pricey but that kind of takes the cake.