There is No Where else to get these at the moment.
the Weight is Perfect - 28g for Bottom Fishing
I use them with an 80lb Test SPRO RT Flourocarbon Leader - and found them Flawless for a Knocker Rig. They are very Aerodynamic, and get my Bait easily around the 50 mtr mark, and If there isn't any much wing ... I can touch 65 mtrs easy.
Though some say, egg sinkers can cause abrasion to leader ... So far, I haven't yet faced this issue with my Knocker rig, using these Sinkers.
I'd definitely Suggest them if you are into Sliding Sinkers.