You always need to be wary when buying Oxalis for the rockery as some are very invasive. One such is Oxalis depressa, a lovely little yellow flowered bulb that we confine to a trough but I dread to think what would happen should it escape!
After the warning, there are a goodly number of small, bulbous oxalis which mostly originate in South Africa. This means that they need very good drainage and some benefit from protection from too much rain during dormancy. Some examples that you might look out for are Oxalis lacinata; O. obtusa and O. flava but you would probably have to search the specialist bulb suppliers to find them.

Easiest ones to find and grow are O. magellanica and O. enneaphylla which comes in various forms.
Did think O. depressa was pink though.

Think you might be right, Owdboggy! There is a white form but ours are pink.