They should be, but they seem to be cheaper in the US market than in the UK market (as with so many things, sadly).

I'm quite tempted to instead pick up the TTL/Spot metering prism from Kiev, the latest ones are made to work with 3 LR44/AG13 batteries and it would be nice to have a TTL meter (I have a handheld Sekonic but it does slow down things a bit).