bilstein makes a good gas shock designed to work with the EAS, many report that it's too harsh a ride (including me). I'm running terra-firma's now, and love them. They do a set specific to the p38 as well.
Either is fine... just find a set that suits you... Bilsteins are quite harsh but good for handling... Original "stock" Boges are comfortable but tend to be a bit soft... Terras are supposed to be a very good "in-between" but I haven't tried them yet..
I'm running Bilsteins on my 2" lifted P38 and would like them to be a bit softer for on-road comfort... off-road, they are great.
Speak to "JeremyD" who's in town your way next week and he might be able to provide local feedback on suitable replacements !
The biggest hurdle from your end is finding a supplier who can source some of our suggestions we may make, otherwise it's an expensive exercise to get what your looking for Stateside or from the old country and what about if you need to get one fixed ?
Give us an idea of any type of terrain covered and the driving style you do in Namibia or whether your truck is loaded or empty.