Pro Tec makes good quality horn cases (normal or detachable bell) and gig bags at a reasonable price; their web site also offers other horn accessories (mouthpiece pouches, valve oil, and a mouthpiece protector.
CardoCases - very slick web site, complete with video demos (in English und auf deutsch!). Handmade cases for horns with detachable bells: Alexander, Cornford, Dürk, Schmid, Fehr, and others (we suppose). Case models each have moviesque names: Route 66, A Night at the Opera, Casablanca, Hemingway’s Dream, Space Cowboy, A Woman’s Secret. The company claims that the cases are as protective as Marcus Bonna cases, but lighter, shorter, and holds more. Check them out and decide.
Horn Guys offers fine horn cases made by Glenn Cronkhite, Marcus Bonna, Protec, and Eastman Strings
Ken Pope, our nomination for retail MVP, offers horn cases by Marcus Bonna for fixed and detachable bell horns. Some samples depicted below:
Sorley's Horn Shop offers a custom horn, instrument cleaning and repair, and Marcus Bonna cases.
Berp.com offers not only BERPS, but also horn "bags" (sic) made by Bags of Spain. Left to Right First row: Eco Bag, Detachable Bell Eco Bag, Detachable Bell Flat Eco Bag (meets airline carry-on size restrictions); L to R, 2nd Row: Detachable Horn Eco Bag with Mute (also available in Geyer wrap size), Detachable Bell Super Bag(s).
Thompson Music offers cases and gig bags by Marcus Bonna (below L), ProTec, Reunion Blues, and SKB (below R).
Patterson Hornworks offers the full line of Marcus Bonna cases (along with a lot more!)
Rayburn Music offers Marcus Bonna cases: MB2, MB, 4, MB5st, MB7, MB8. So does Sorley's Horn Shop. You might want to visit the MB itself to check out all their offerings.
Dillon Music has Pro Tec cases for detachable and regular horn bells. You also buy them direct from Pro Tec itself.
Woodwind & Brasswind. Great selection of cases (among other things): Pro Tec, Gator, Atkinson, Gard, Reunion Blues, Altieri, Giardinelli, SKB, Soundwear brands.
CaseCAD - If you travel by plane with your horn a lot, you might consider getting a hard case (e.g. by Pelican or Anvil) and get a custom case insert. This company offers a free CAD software download (PC only) so that you can design foam insert for hard-sided equipment cases. You design it on the computer, email the design to them, and in less than a week you have your precision cut foam insert for your hard case.
FineCases.com offers 6 model of horn cases: 2 Gator cases (see above), a Guardian case (thermoplastic) - see below, L; 1 Galaxy (see below) and 2 ProTec.
Horn maker Alexander also sells a variety of cases (also Marcus Bonna cases).