Hi Donald,
If you plead guilty, this will be a conviction recorded in your criminal history. You have an arguable case that you were not acting dishonestly. Speak with a lawyer or apply for legal aid.
At the end of the day, it comes down to how well you present your case in court and how believable you are. If you think you can present it eloquently, given it is for a small sum of money, you can try self-representing. I suspect the estimated cost of $6500 is for an appearance in court. Call around other lawyers and get other quotes. Most law firms offer free consultations for the first meeting, take advantage of this.
If you don't have receipts, have you ever paid by card at this store? If so, check your account statements and highlight every time you have made a transaction to this store. Are there shop assistances or local shoppers who recognised you from before?
A reasonable magistrate will understand that if you put something in your pocket, you may forget about it later on. Explain to the court why you put the items in your pocket, what you were doing at the time. Did the items clearly have security tags on them? Were they hidden pockets or fairly visible pockets? If you did intend to steal something, it would make sense to cut the tags off, or take something that didn't have security tags on them, and hid them in a bag or hidden pocket so it is not visible. Where were you in the store? How did the store detect that you stole something? Did you do this in front of a security camera? If so, wouldn't this appear inconsistent with the profile of a shop theft?
If you made a request to pay for the goods to the police, tell the court this. Identify the police officer to whom you made this request. Have you spoken with the store and offered to pay for the stolen goods? You can write a letter to the store expressing your apologies for how things turned out, state that you did not intend to steal and offer to purchase the goods from the store. Careful to not admit guilt (if you intend to fight the charge), but try and be helpful, understanding and offer to resolve the matter with the store manager directly. You can then submit this letter to court to support your claim that you meant to harm to the store.