With the exception of the GTA all 147s with vented discs use the same brake pad.
The lower power 1.6TS 147 only has solid discs and uses a different caliper & pad.
Early (pre 2001) 156 1.6TS, 1.8TS & 1.9JTD also used solid discs and used a different caliper & pad to the vented setup on 2.0TS & 2.5V6.
If your 1.6TS 147 has vented front discs it will use the same pads as:
post 2001 1.8TS 156
post 2001 1.9JTD 156
and many many others too, it is a pad used by a large part of the Alfa/Fiat/Lancia range both past & present.
In comparason, the pad used with the solid disc 147/156 is only used in those cars and is not shared by any other car in the Alfa/Fiat/Lancia range.
As for which pads to go for, the ideal is DS2500 front with DS-Performance rear, however the rear pads for 147 & late 156 is not available in the DS-Performance compound.
As you are not looking for a big upgrade, I would go for Ferodo DS-Performance front with Ferodo Premier rear.
As for a supplier, try: www.motorsportworld.co.uk
The discs will probably need to be changed at the same time, EB Spares do some at a very good price: www.ebspares.co.uk