Need a shipping box for Technics SL-1200-MKII

Find a UPS Store near you. They will pack and ship it for you. If anything happens to it, it's all on them.

do what what abucktwoeighty says .

I wouldn't trust UPS to pack a table. The tonearm needs removed (cartridge first). Then, the dust cover needs removed and packed separately. If the platter comes out, that should get pulled.
Now, UPS or any monkey can pack it all up safely. Keep in mind that packing and shipping the arm and cartridge takes a little care. A broken needle will ruin all. Once you get it there, you do know that setting it back up will take some skill.

Go to mrboxonline.com. They will custom make any size box at a reasonable price and send it to you. They also have packing materials.
I purchased made-to-order double boxes and styrofoam sheets from them to pack & ship a pair of Dunlavy IV-A speakers to England. Nice price and nice people. (Fortunately, for me, they are local and I could pick up the boxes.)