The interior dimensions for RockCase for bass by Warwick Universal is Length : 46-1/2 in. Height : 14-5/16 in. and Width : 2-7/8 in., so the height (which is JM width) works. Online price is $79.95. Coffin bass case seems to be $129, so looks like RockCase is most reliable bet, as it is returnable, and Rondo is not. his seems to be best priced option of all.
http://www.zzounds.com/item--RCKRC10605B