I bought one of the eBay MX half-cases, and it is quite nice. The bottom is quite thick (I think for structural reasons because the MX base is so thin and close to the lens) so it makes the MX feel larger - but it still handles well. However, after I bought it at $62.80 they raised the price for new orders by $100 - so no longer the bargain it was.
Wow! $162 USD? I have been mulling the idea for some time of producing a line of "Made in USA" half cases. Perhaps now is the time. There was about a 20-year period when most of the cases sold with Japanese cameras were pure junk. Almost all have long-since disintegrated into dust. A decent replacement half-case can significantly enhance handling and can provide much needed protection to our precious vintage gear.
Some less expensive alternatives are the Horusbennu (Korean) MX eveready case or aluminum grip, both available on eBay.
A Pentax Winder MX (also inexpensive) makes this diminutive camera handle better, too. I bought mine from KEH.