I suspect you might want a field of view at least as wide as the Celestron X-Cel LX you have, so I am not recommending 50 degree field eyepieces.
In 60 degrees, it's hard to beat the Astrotech Paradigm (available in the US or in Europe as the BST or Teleskop Service NED).
In 68 degrees, the Explore Scientific 24mm or the Baader Hyperion 24mm are great eyepieces, and might fit your range if found used. Ditto for the Meade Series 5000 SWA 24x68 (1.25"), the Meade Series 4000 24.5mm (1.25") SWA.
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