My own experience is that a low A needs to be a .145 or larger to avoid excessive floppiness and flabby tone. So for a whole step down you could build a custom set of singles from one of many mainstream brands that do a .145 (D'Addario, Ken Smith, Warwick etc.). A light and equal tension set would be something like 145 105 80 60 45 32. If you're in the USA:
Build your own string set!
For 2 whole steps down it's either Circle K Strings or custom made strings from
Octave 4 Plus.
Circle K also sell 'traditional tension' sets
Circle K Strings - Standard Traditional 6 Strings where the tension gently rises from low to high, these will be slightly closer to the mainstream 'top heavy' sets you are probably used to. However i recommend the 'balanced' sets, there are many advantages as i see it.
You can use the CKS tension chart to discover what tension you like, and then use this value to choose your set. The chart can be used to approximate the tensions of other brands so you can also use it to design a custom set of single strings from another brand.