To acquire the bed, you can buy it from the carpenter shop for 1000 gold, or spawn it into your inventory by typing:
dga_add "aedenthorn.PetBedDGA/Pet Bed"
directly into the console and pressing Enter.
To have your pet sleep on the bed, use the Custom Pet Beds mod.
A list of all my mods for Stardew Valley is available at https://www.nexusmods.com/stardewvalley/articles/895.