I don't know about those flat strips but wire is procurable directly from Precious Metal Merchants, and I believe any length so it's not like you need to buy a whole roll of wire. 99.9 or 99.99%, but the latter is more expensive of course. The 99.9 is normally around 99.98% so for the extra cost in assay of .2% for 99.99 I get the former, 99.98 is near enough for me.
I bought 1 meter, so I'll never need to worry about replacing electrodes, that amount will definitely outlast me, and avoid any increase in silver price as time goes on. Price fluctuates so watch the market and buy when you think the price is suitable.