I received one of the basic sleeves each from CollectorKnives and KnivesShipFree. The Frontier Bone 43 is simply too thick for the CK slip while the narrower 43s (camel bone, jigged green bone, etc.) seem to fit but require some effort unless the slip is already broken in. The KSF slip which came with my 43 fits the camel bone and green bone absolutely perfectly. I haven't tried it with the Frontier Bone 43 yet, although the KSF slip does seem to be a little roomier overall so it might accomdate the thicker bone.
I haven't bought any of the GEC slips.