As already mentioned you should be able to replace them with three AA's (HP7's), granted they won't last as long but they are more readily available and significantly cheaper - even Duracell AA's are cheaper. Rapid Electronics stock a 3xAA holder but I can't find one at Maplins. Rapid are a bit expensive once postage is factored in as they are mail order only. Maplin are high street so may be a better choice. The do stock the 1289 for £1.99.
<NOSTALGIA>Who remembers PP3, HP7, HP2, HP5 from Ever Ready - none of this poncy AA stuff