One asks an oral solution Calcium gluconate 10%

A solution of calcium gluconate 10% is an oversaturated solution. The classic method of avoiding crystallization is the addition of 0.36 G Ca-D-saccharate.

Cagluconate 9.5% + Ca-D-saccharate 0.36 G water up to 100 ml  

This product you are not going to find at the classic suppliers of pharmaceutical raw materials.

Maybe this solution exists as a commercial preparation?  

It is perhaps easier to prepare a solution with the same calcium content with calcium glycerophosphate. If the amount of calcium glycerophiophate does not dissolve completely, you can add citric acid for each gram   calcium glycerophosphate 0.5 g.  

Given that we have to do this with an oral solution, there is also the possibility to prepare a suspension with BV Avicel RC 591. See Galenic Formularium.