I read some references that suggested you could invert sugar by cooking it with some acid like cream of tartar or lemon juice but I haven’t tried it. Please let us know how it works.
Here is a citation. It is vague about quantities but does give some guidance on the best heating method.
As shown in the formula, sucrose may be hydrolyzed into invert sugar by either weak acids, such as in cream of tartar (the acid salt of weak tartaric acid), or by enzymes, such as invertase. Each is described below.
acid+heat C12H22O11+ H2O −−−−→ C6H12O6+ C6H12O6
Sucrose Water Glucose Fructose
In acid hydrolysis, it is both
(1) the amount of acid, and
(2) the rate and length of heating that determines the quantity of invert sugar that forms. This is addressed below:
• Amount of acid: Too much acid, such as cream of tartar, may cause too much hydrolysis, which forms a soft or runny sugar product.
• Rate and length of heating: A slow rate and slow attainment (long length of heating) of the boiling point increases inversion opportunity, whereas a rapid rate provides less inversion opportunity.
In enzyme hydrolysis, sucrose is treated with the enzyme invertase (also known as sucrase) to form glucose and fructose.
CULINARY ALERT! Enzyme hydrolysis may take several days, as is the case with invert sugar that is responsible for forming the liquid in chocolate-covered cherries.
The glucose that forms from inversion is less sweet than sucrose and the fructose is more sweet, with the overall reaction producing a sweeter, more soluble sugar than sucrose. Invert sugar is combined in a ratio of 1:1 with untreated sucrose in many formulations to control crystal formation and achieve small crystals.
I found a French supplier of commercial products.