You should get plenty help very soon, this is a very common remedy for wi-fi only ipads.
Personally I'd rather buy a used 3g/gps
ipad to maintain the convenient portability of the ipad, watt usage, airtight waterproff cases, etc.
Craigslist has many
cheap afordable ipads, I'd think you could get an ipad 2 3g 16 or 32 gig for $150-$300.