I am by no means an expert but your best bet are fundolpanchax gardneri, nothobranchus guentheri & nematolebias whitei. Rather than relying on shops, consider joining the British/American Killifish Association as they provide lists of members as well as who has what for sale. It is also a great place to improve your knowledge. Big C is really worth having a chat to on this forum for knowledge. Sorry about the lack of common names but the killi nuts will know what you are talking about.
Website for the above associations: http/www.bka.org.uk/
http/www.aka.org/