OK I don't know if this is the correct place to post this, but it seems like the closest fit so here goes.
I am going crazy looking for a heavy cardboard box that will fit a couple 4ft. T12 fluorescent tubes  in them with sufficient room for bubble wrap/packing peanuts to guarantee safe shipment, so I figure 50"x6"x6" or some such... but I have tried the local hardware stores and they all say they crush their boxes immediately after stocking and can't save any empty ones.
I've also checked local storage and moving companies and all they offer is squarish-size moving and bankers boxes.

I have a pending trade and this is holding me up sending the item.
If anyone has any suggestions or ideas please let me know.
Thanks very much!

If your looking to Ship couple of 4 foot  T12 tubes best cheap way to do this is put two  fluorescent tubes in a 4 inch PVC
 Pipe  by using strips of Egg foam  to space the tubes out inside the inside 4 in PVC plastic pipe.  Then add bit foam on each end.  And use card board Disk on end of tubes and use duct tape.  I have sent 8 foot fluorescent tubes from UK to Texas doing this method.

Maybe an electrical supplier would have an empty fluorescent lamp box.

Tip- when sending tubes, don't use a rectangular box. As funkybulb says, a thick walled tube is best, I've had lamps packed in 4in diameter drainpipe..! If you can't get a tube, cut one edge of a rectangular box lengthways and fold it so it's triangular in section. This is much stronger. For packing materials, shredded paper is good, but bubble wrap is ok,but you must remember to allow a little "wiggle room" - the lamp should be free to move ever so slightly, but not so much it makes contact with the box walls.

Hope this helps.

You’re best bet is to ship them bubble wrapped together in a large
Thick pvc pipe - I’ve received many fluorescent bulbs this way over the years with out incident,

I even had a 1970s Sylvania F90T17 sent to me in black heavy pvc
Without any problems,

Shipping long fluorescent bulbs in heavy pvc pipe from my experience
Is the best way to go and make sure You allow 8 to 12 inches for extra packing on each end to with stand those vertical drops if they should occur ,

Good Luck !

Hope this helps ,