Why do you want a UV-A light. It is pretty pointless getting just a UV-A light as will give you marginal results. The wonder frequency is UV-B, or to be more specific, 310nM. You can buy reptile lights that are good for small spaces. Otherwise its Solarcure or Migro which will sell a 2ft unit with high UV output. Good enough for a 4x4. £40-£100 for any of those, depending on what you get.