Mega IT Stores - Did not supply as per contracted

MEGA IT STORES sold me a Refurbished laptop computer through Takealot which is missing an important part . After having received their payment, 21days several calls and emails later they are trying to weasel out of delivering what is due to me.
This computer was purchased specifically for the feature of the built in pressure sensitive active stylus which was missing on delivery. The computer was purchased as "Refurbished". One expects scratches and wear but if it is “refurbished” i.e. reconditioned, made good, renovated, it should have all important parts and be fully functional.
First they tried to invoke a disclaimer (which was not published on the Takealot site but on their own website ) that the part is an accessory which it is not.
They later tacitly acknowledged their need to supply the stylus by suppling a cheap non-pressure sensitive capacitive stylus which is not a comparable substitute.
I have given them information and examples of comparable replacements and where to get them, and I will even accept if the substitute does not fit into the computer for charging if it is functionality is comparable. The value of the missing part is approximately R695 of a total charge of R8295.
Their reply is to offer yet another cheap non-pressure sensitive capacitive stylus which is no better than using one's finger and is not pressure sensitive. As IT suppliers they should know the difference.
I do not want to cancel the contract as I have already spent time setting up the computer and I prefer the silver colour option which is not commonly found.
I have a legal right to due performance rather than cancellation of the transaction as this is reasonable and easy for them to achieve.

I have used Takealot in the past and had good service, I would like Takealot to put pressure on their supplier to act honourably, reasonably and deliver what they sold.

I will accept a credit to my credit card for R690 and source the part myself if they do not wish to do it themselves.