There are nasty, cheap, plastic options available in supermarkets. I had some from Tesco's, I believe (bought on my behalf, so I could be wrong).
A question that doesn't seem to arise often - what on earth is in your under-counter cupboards that may kill a toddler? Is it just the evil chemicals under the sink? What not move them for the duration (or permanently, if it is a danger). Plastic and metal pots are brilliant toys for kids - add a bit of water and you have instant child entertainment. Without water you have noisy entertainment.
I child-proofed my cabinets, and always regretted the decision - had to screw nasty white plastic things to the insides of doors, and they are still there, even though the toddler is now 11. Toddlers grow faster than you think, and dumping a large pot on their toes is a valuable life lesson for any child. Why ruin your cabinet doors for a very transient problem? Obviously the female contingent will hit the roof with this logic, but you can win them round by just....not fitting the door locks, and discovering that nobody died as a result. Promise faithfully to do the job, but finding parts, time, delivery issues, etc...