We need more/better description to know what might work and what won't. Is the trike a tadpole or a delta? If tadpole what's the hub brand. If a delta the bike's brand and whether the axle also is the driver or the follower one . Deltas generally only have one wheel driven, usually the RH one here in a country that drives on the RH side of the road (the RH drive helps counteract the road's crowning). This type of axle will likely be specific to the trike brand and possibly the model too. I assume the shop you bought it from is of no help? Have you contacted directly the company that made it? Andy