shipping boxes for heavy electronics

greetings, first post here on audiogon forum. I have a heavy parasound amp that is about 90 lbs, and I do not have original shipping boxes. I took it to fedex and they said they would have boxes for the dimensions of the amp, but not for that weight, as their heaviest box can withstand 60 lbs. I have been looking on the internet that would have a rating of 80+ lbs, but I simply cannot locate one.

Can someone make a suggestion on where to acquire such heavy duty shipping box for electronics? any suggestion would be greatly appreciated. amp dimension is 19"x8"x20".

Thank you.