I was asking myself the same question the other day. Bear in mind that I have owned my gun all of seven months, so treat my responses with that in mind.
After getting the gun, I bought a basic bore snake, some Napier cleaner in a spraycan & a tube of Napier VP90 grease - all from an online store. Along with some simple cleaning cloths, that seemed to take care of all of the basic tasks.
Since then, I bought a
Beretta cleaning kit from the gun shop in Chichester. This came with a rod, wire brush, spiral brush, mop, jag, patches, oil, grease, rubber gloves, snap caps (best not mention those around here), small brush & microfibre cloth.
I was really only after the rods, jag & wire brush, but the additional items seemed like added value (for example, the Beretta oil & grease bottles are available separately, but around £9 each), plus everything packed away into a useful storage case. I compared the Bisley kit with the Beretta version in the shop, and in my opinion, the Beretta items looked better quality. I probably could have bought the parts more cheaply individually (though not from Beretta), but here they all were, in one box.
As Will said earlier, no kit will probably be quite right, but it will give you all of the basics, plus somewhere to store the parts (depending on what you buy).