I'm probably missing something, but in the episode REDEMPTION PT. 1, Worf resigns his commission to join Gowron and serve on the IKS Bortas. He lays down his com-badge in the observation lounge, and in the next scene he's in his room packing his stuff--wearing a full grown Klingon military uniform!
AFAIK Worf never joined the KDF, so they certainly didn't give him one. If his dad died at Khitomer, presumably he (the dad) was wearing his uniform at the time and it's got holes and disrupter burns. I know he somehow held on to the bat'leth that was in his family for like ten generations, so I suppose it's not a stretch to think he could have inherited or obtained a uniform from a friendly Klingon family.
I think I remember on DS9 Rom had a Starfleet uniform made for Nog before he set off to the Academy. Did Worf just replicate a cheap Earth knock-off Klingon uniform? Maybe when he was younger and researching his culture?
I know he wore a different uniform in THE EMISSARY to talk down the T'Ong, but that was just a ruse to convince the T'Ong not to freak out.