If UK immigration find one in your bag, you will lose it.Yes, they're brilliant - if used sensibly, which many people do not. People commonly point far too close to the bird and then are surprised when it promptly flies off.
I bought my last one 7-8? years ago which was minutes before they (viz. properly-bright green ones) were (apparently) banned from commercial sale in UK. So you will probably have to cast your net wide and to less-regulated lands.
'Trading Standards Authorities may use their existing powers under the General Product Safety Regulations 2005 to remove laser products intended for consumers of Class 3B [5-500 mW = mine] and Class 4 (as defined in the British Standard) from the general market.’There is no such thing as an illegal laser pointer in the UK.
I have a new American made Class 3A 5wW green pointer for sale. It use two AAA batteries. I have posted it on For Sale pageHi. I'm off to Belize in a couple of weeks and it will be far easier to get my partner onto birds using a green dot laser pointer than verbal directions, similar to what bird tour guides use. Does anyone have any experience of recommended models/brands? Thanks