* Prices may differ from that shown
I have loads of these Arcadia controllers in various wattages, for various beasties. I use them for my tortoises' UVB tubes, as well as tube lights for other critters. I have found them to be very long lasting, very robust and the actual starters are simple and easy to replace, when needs be. You can buy them in any DIY or hardware shop, they are the very same as what you would use for overhead strip lights in the kitchen or garage. Just make sure you get the correct grade!
They are simply a grey box, with a large section of the front taken up by vents; through these vents you can see product information, such as wattage and amps etc stamped on the inside. At the other end it is rounded, and this is where the actual starter sits. These have two white rubbery end caps, one of which is on a longer length of cable, to allow for the convenient positioning of the unit while a bulb is mounted within it (picture it in your head with a 4ft tube attached and you'll see this is handy!). I love this feature, it really is better than if the cables were the same length - you would either have not enough cable on one side or too much, and it would really dictate where the controller would have to sit. This could be very annoying as the unit has a switch on the side of it, so you can control it without needing access to the wall socket.
You do get controllers specifically for use in high humidity environments (Ultra Seal), and these claim to have a superior seal around the ends of the tube bulbs. However, I have used the regular ones on turtle tanks and they have been perfectly fine - though turtle tanks should never be overly humid (as they should be open topped), the end caps could still get splashed, or get some water drips gathering on them. Care must of course be taken when using any electrical equipment around water, but I have found using them in these circumstances to be absolutely fine.
The unit itself is surprisingly heavy, so try to ensure you place it somewhere secure. They also get very hot during use, but this is normal by all accounts, and mine have been getting warm for years (on for 12 hours daily) with no adverse effects. During all the time I have been using these, I have never needed to replace a starter yet. I keep pulling them out my cupboard when I'm expecting a new addition, and assume that I'm bound to need a new starter this time, but as of yet no! They have also survived a few butter fingers moments with nothing more than a clunk and a few scratches.
They come in a variety of wattages and although you must not use a higher wattage bulb than the unit is rated for, I have used lower wattages loads of times over the years and it seems to cause no problems. I have argued the toss over this with fellow hobbyists, who think you MUST match the bulb wattage exactly to the controller wattage but I've simply never done it, and I've never had a bulb (of any brand) blown, flicker, cut out or just stop working in any way.
In terms of prices it varies with wattages, but for a brand new one you're looking at around the £15 mark as a minimum. Another thing it's worth shopping around for. I got all mine used from a variety of online places for far less. Just remember to factor in P&P costs from private sellers such as on eBay, as these are heavy items. In my experience though they last brilliantly, can take a few knocks and as I mentioned I haven't even replaced a starter yet. Arcadia is a brand I trust 100% when it comes to controllers, as they seem to have been the dominant one in the market for as long as I can remember. And I think it's well deserved.