One option you could consider would be to make your own leather accord. If you want to do that a great place to start would be the Perfumer's Apprentice Leather Accord which you can also buy ready-made from them if you prefer. The Safraleine included in that accord is a wonderful material that I use often and is the key to it.
An alternative is Cuir Base 184028 by Firmenich, which is excellent. Another material I think is really good in this area is Suederal LT by IFF which smells just like new suede to me.
I have stock of Safraleine if you have trouble buying it in the quantities you need but currently not of the others (though Suederal LT I'm likely to re-stock over the next few months).