Specials is designed to turn off when there is a products_id in the URL ...

You can change this with your templates and overrides by copying the:
/includes/modules/sideboxes/specials.php

to your templates and overrides directory:
/includes/modules/sideboxes/your_templates_dir/specials.php

and adding the code in RED:
Code:
  if (isset($_GET['products_id'])) {
    $show_specials= false;
  } else {
    $show_specials= true;
  }

// bof: force specials to always show
  $show_specials= true;
// eof: force specials to always show

  if ($show_specials == true) {
For the Best Sellers sidebox you can customize it similarly with the code in RED:
Code:
  } else {
    $show_best_sellers= true;
  }

// bof: force best_sellers to always show
    $show_best_sellers= true;
// eof: force best_sellers to always show

  if ($show_best_sellers == true) {