I bought a Pitmaster IQ-110 several years ago and still use it regularly with my Weber. It works well and does what is claims to do. I bought mine directly from John in St Louis though as I happened to me passing whilst driving Route-66. You can buy them directly from the PitmasterIQ web site for delivery into the UK. I regularly do this with other US based BBQ suppliers and it usually only takes a week or so to arrive. The shipping on the IQ is about £55 (£36).
There are others available though that do a very similar job. I know others who have the QMaster Senior - which does a very similar job.
http://allchinas.com/senior/Senior-Manual.pdfLots of clips on YouTube about both.
How are you setting up the minion/snake in your Weber? When I am not using the IQ-110 I use this method all the time and it works well. You do need to use good quality briquettes for it though in order to get the long and consistent burn. These days I only use Heat Beads in conjunction with different flavoured wood pellets.