The Julius K9 harness can have pannier attached to them, I have a Doxlock Harness with some panniers but haven't used them as they are likely to get ripped off on a bush by the Springer.

Well, the excursion backpack arrived today. It's comfortable and a good fit on him. But with a plastic D-ring and thin fabric strip and one point going round the front of the dog, not a hope of it holding a strong dog, so looks like he'll be walked on his collar whilst he's wearing this.

I'm disaponted, I could have got a cheaper backpack to do the same job, or saved the money towards buying a better quality one, you live and learn.