Gary, you could try something like the tri people use. Something like
this shouldn't be in the way for cx (remove the bottle) but would mounted and ready to hold a bottle when you ride on the road.
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The Lord is merciful and gracious, slow to anger and abounding in steadfast love. - Psalm 103:8
I am a cyclist. I am not the fastest or the fittest. But I will get to where I'm going with a smile on my face.