Had exact same problem last year. Posted same question last year and got
following answer. It also completely solved the problem of numbness.
Extremely well constructed and currently has around 300 nautical miles of
ocean use. Highly recommend it.

SealLine Kayak Thigh Support Cushion
$39.95 REI Item 722799
http://www.rei.com/online/store/Prod...atalogId=40000
008000&productId=47901036&parent_category_rn=45014 87&vcat=REI_SEARCH

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Big Island Bob