The OED lists only stridden and coll, strode. I would always use "have stridden" and I see "I have strode" as dialect in the same way as "I have ate" or "I have took".
However, looking in the online corpora, among their very few instances of any form of stride, there are hardly any instances of stridden at all (figures for "stridden/strode" immediately following any form of "have"):
- NOW: 4 stridden, 44 strode
- GloWbE: 0 stridden, 15 strode
- COCA: 1 stridden, 4 strode
- COHA: 4 stridden, 19 strode
- BNC: 0 stridden, 1 strode
So my conclusion, rather to my suprise, is that strode appears to be much more common as the pp of stride than stridden, even in the historical corpus (COHA). This applies in both US and international corpora; and the only specifically British corpus (BNC) hasn't enough instances to be significant.