A proper flight case for that amp,(Anvil, Calzone etc), will run you around 400 bucks new I think. I bought an Anvil flight case for my Hiwatt DR-504 head about 14 years ago, and it was $349 at a discount new. I have never once regretted buying it, and has done a remarkable job of keeping the head safe and pristine. You can find used ones on Ebay sometimes, just look. Two years ago I found an ATA flight case for my 360/12 that was form fitted in mint condition. It's as about as good as it gets, and a comparable ones started at $450, and ones with as nice an interior and features were $100 and more. I paid $150 for this one, and am quite happy with it. Who knows, someday I may even use it!
Music Go Round is also another good choice. I bought a Roland JC120 for dirt cheap because the reverb wasn't working. They boxed it up and shipped it very inexpensively. Replaced the shorting tank wires, and the reverb works just fine now. Music Go Round also has a ton of used road cases, just go on their website and you can both look and purchase nationally. I'm sure there are others, like Craigslist, that can help you out, but I have no experience, so I can't recommend.
When people don't need these things anymore, you can get them less than half of the new price. Do not waste your money on a junk case.
FWIW, SKB makes a really good amp case designed to fit a variety of amps. I used one of those to ship an amp from Los Angeles to Norway a few years back and it worked great. I think those are around a couple of hundred bucks, but you can use them with any comparably sized amp, instead of a case made for just one.
Play loud!