As an alternate strategy to Ben which had a good template, I would propose to send a follow up email which does not directly refer to your original email at all. First, based on your proposed emails for the follow-up, there's some odds that your original emails were dismissed for cause (i.e., they had issues). Second, if they did not see your prior email, then including the prior email on the thread is a nudge, even if you never refer to it. It says: "Hey, I tried before and you didn't get a response." Sometimes this is what you want, to add a bit of pressure, such as when bothering an admin where a paper trail of non-responses will help light a fire if you need to escalate the issue.
In the current case (and for professors in general), you're asking for a favor you messaged during the middle of the most prevalent religious holiday in their country, so including the prior message in the thread will definitely not help you. I would say don't include it and don't directly refer to it. There is no upside. They either already dismissed you (and will again) or you will be highlighting to them that you messaged them days before Christmas and actually expected a response.
As a proposed contact.
Dear Professor [NAME],
I hope you had a good holiday break and are doing well.
I hope it is not a bother, but I was writing to see if there may be
any opportunities for a PhD candidature under your supervision in the
upcoming year. I have attached my CV and previous experience.
If you think I might be a suitable fit for your program then I'd
appreciate an opportunity to talk more about this and to read any
articles or whitepapers that reflect your current directions.
Alternatively, if you think my background is not suitable, I'd love it
if you could send me back any critical appraisal of weaknesses or
skills that I could build which would make me a better candidate (or
even just reply to let me know I'm not a good fit).
Thank you so much for your time.
[NAME], Pestering PhD wannabe
[No prior email chain. Nothing here. But attach your CV and whatever
else you're giving]
This is sufficient to alude to the prior email (it references the break, which excuses them for not responding) and it apologizes for bothering them.
Then, before you send anything, have two people look it over: someone who is ideally somewhat familiar with the academic culture of where you are sending it, and a second person who is good at French.
With that said, rather than starting by cold-calling professors: I would encourage you to look for the CV's of the students who are currently in the labs you are applying to. Take those CV's, cross out everything that happened since they started the program, and compare your CV to those CV's. What are you missing? Are you actually at all competitive for where you are inquiring? It's fine to inquire at a few places that are a reach, but you need to know where your standing is: if you're well-below where the average accepted applicant is, you need to own that and know where you stand when you contact. People are more likely to respond if you're actually closer to a fit and if you have reasonable metacognition of your strengths and weaknesses.