Maybe you could take portraits from here and pass them through an AI image 2 image diffusion workflow with a pixel art addon, just to sprinkle some detailing on the existing structure, with a low denoising strength perhaps 0.15~0.35.
I would recommend doing this in Forge webui with this extension for the pixel art part as it is the best one I have found for myself trying to create a full text2img Stardew character generation workflow.