You should for purity’s sake bin the non-Naim source ang get a Naim source. If you are a proper Naim nutjob then it’s traitorous to infect the PRAT chain with illegal aliens. Don’t PRAT about. For the love of Naim, do the right thing.
I have a variety of non-Naim sources and in all cases I have found the old Chord Chrysalis or the Naim lavender/grey RCA -DIN interconnects to be my favourites. They just work really well in a Naim system. Although Chrysalis is discontinued by Chord, you can still pick them up secondhand pretty easily. It was replaced by Chord Crimson, which is fine, but I much prefer Chrysalis.
I only have one source that isn’t Naim and that’s my Orbe SE/SME V/Dynovector DV20-X2/Dynovector P75 MK 3. Over the years i have tried numerous cables and always come back to the Naim lavender RCA-DIN cables. In fact, the only cables that are not Naim in my system are the 8.5m runs of Chord Epic X.
Another good interconnect that goes superbly with Naim especially when using NACA5 speaker cable are DNM interconnects. They are pure copper, come in DIN, RCA combinations and are relatively cheap, but sound gorgeous with superb detail and mids. (In terms of a natural sound with no added brilliance or highlighting.)
You can also get versions with RFI filtering, they cost more, but I find they really work for me.
I am listening using DNM RCA to DIN now between my DAVE and Nait50.
I suggest that you just get in touch with a respected Naim dealer in the UK - say Cymbiosis in Rearsby (Leicestershire) or Grahams HiFi in Islington (London) - who must be able to supply a Naim or Chord cable, terminated as you wish.
(As you’re non-UK resident, they may even to deduct the VAT from the purchase price, but I don’t know about that.)