We make full scabbards both for our own swords and as custom fit for customer's own swords. In recent years we've also been cooperating with some of the weapon makers to provide scabbards to fit their swords which are sold on the same Larp circuit we trade at.
It all started when customers came in asking for scabbards that would work with a particular style of sword which was heavily counterwighted. This makes the sword fast to wield but meant that the sword was always trying to tip forwards when it was on the hip. We came up with a scabbard made of a slightly heavier leather that counterbalanced this tendancy and changed the strap mounting points so the sword sat naturally on the hip.
A full scabbard is also a good idea to protect the sword from accidental knocks when it's just being carried around, especially at fest type events where it's being worn a lot more that it's being used.